Malombra.

Gothic and erotic mystery about a young man called Marco, who goes to stay with his strange uncle, whose wife (Marco's beautiful aunt) died some time ago. His uncle's sister-in-law is the only other person living there. Marco spies on rituals of self-gratification performed every night by a red-headed woman who looks just like his dead aunt! Marco begins to wonder if the woman is actually the sister-in-law made up to look like her dead sister, or the dead aunt haunting the place